The present application relates to a microparticles measuring apparatus and, more particularly, to a microparticles measuring apparatus which detects a leakage of sample solution and sheath solution and thereby suspends the operation automatically.
There has been an apparatus used to optically identify the characteristic properties of such microparticles as those associated with living bodies (e.g., cells, microorganism, liposomes) and any synthetic microparticles for industrial use, such as latex particles and gel particles. It is so designed as to introduce a dispersion of microparticles into a flow channel and direct a light beam to the microparticles passing through the flow channel.
Most popular among apparatuses to measure microparticles associated with living bodies is a flow cytometry, which is called a flow cytometer. (See “Saibou Kougaku (Cell Engineering), supplement volume, Experiment Protocol Series, Mastering of Flow Cytometry,” by H. Nakauchi, issued by Shuujunsha, 2nd edition, issued Aug. 31, 2006, referred to as Non-Patent Document 1 hereinafter.) One type of it is intended only to identify the characteristic properties of microparticles and the other is designed to fractionate microparticles with desired properties according to the results of measurement obtained by the first type. The latter which is used to fractionate cells is referred to as “cell sorter.”
The flow cytometery in the related art is so designed as to determine the characteristic properties (e.g., size and structure) of such microparticles as cells and microbeads in the following manner. A sample solution containing microparticles of interest is introduced into the center of the laminar flow of a sheath solution passing through a flow cell, so that the microparticles are lined up in the flow cell. The microparticles passing in a line through the flow cell is illuminated with a light beam, and the scattered light or fluorescent light emanating from them is detected for determination of their characteristic properties. This step may optionally be followed by fractionation of microparticles having desired characteristic properties in such a way that the sample solution containing microparticles is discharged in the form of droplets from the flow cell and individual droplets are moved in different controlled directions.
Japanese Patent Laid-Open No. 2007-46947 (referred to as Patent Documents 1 hereinafter) discloses a cell sorter in the related art (as shown in its FIG. 7) which is composed of a flow cell having a flow channel that causes cells (dyed with a fluorescent labeling reagent) to be lined up therein, an optical system that illuminates the cells with a laser beam and detects scattered light or fluorescent light, and a cell fractionating system that controls the moving direction of droplets discharged out of the flow cell.
In the meantime, there has recently been developed a microchip which is composed of a silicon or glass substrate and a region or flow channel formed thereon to perform chemical or biological analysis. The analytical system using such a microchip is referred to as μ-TAS (micro-total-analysis system) or labo-on-chip or biochip.
The μ-TAS may be applied to the technology for fractionation of microparticles which examines microparticles for their characteristic properties in optical, electrical, or magnetic ways while they are passing through the flow channel or region formed on the microchip. An example of the microchip for separation of microparticles is disclosed in Japanese Patent Laid-Open No. 2003-107099 (referred to as Patent Document 2 hereinafter). It is composed of a first flow channel into which is introduced a solution containing microparticles, a second flow channel for sheath solution arranged along at least one side of said first flow channel (both flow channels being formed on the same substrate), a microparticle measuring unit for passing through said first flow channel, and at least two flow channels (placed downstream the measuring unit) for separation and collection of microparticles. The foregoing microchip has electrodes near the transitional part between the measuring unit and the separating flow channel. The microparticle fractionating apparatus based on the microchip controls the moving direction of microparticles by means of their reaction to the electric field of the electrodes, so that it can perform fractionation of microparticles.
The flow cytometery (of microchip type) based on μ-TAS may have the flow channel formed on a disposable microchip so as to prevent cross-contamination of samples during measurement. However, this advantage is offset by the following disadvantage arising from the vulnerability of the microchip and parts in the measuring unit connected thereto. That is, the microchip itself and the connection between the microchip and the measuring unit get fatigued and break after prolonged use, which leads to a leakage of sample solution and sheath solution. This trouble also occurs when the connection between the microchip and the measuring unit cracks under stresses after repeated replacement of microchips.